Treatment Of Aquaculture Solid Waste Using Sequencing Batch Bio-floc Technology System

Bio-flocculation Technology (Biofloc Technology, BFT) was applied inaquaculture through controlling the DOC/TAN in the water. Under the moderate stirintensity conditions, heterotrophic bacteria can deplete the cheap carbon sources (starch,molasses, etc), and convert the ammonia nitrogen to the protein in the form ofbiological flocculation, which can be taken in directly by aquaculture animals such asshrimp and fish. Therefore BFT, which having good economic benefits, environmentalbenefits and social benefits, and is being studied, practiced, expended in many countriessuch as Israel, United States, Canada and China, is considered as an innovation modebecause of its three advantages as followed: firstly, purifies the aquaculture water;secondly, improves the use rate of feed through aquaculture animals’ intake ofbiological flocculation; thirdly, reduces the costs of feed.Total solid suspended particles (Total suspended solids, TSS) can be as flocs’carriers in biological flocculation process. High concentration of TSS is beneficial toflocs’ formation, however, it also bring us some practical problems in recirculatingaquaculture system for examples: high treatment costs, low dissolved oxygen, fish deathowning to the clog of fish gills and so on. In order to solve this problem, we do someworks: first of all, we adopt removed type biological flocculation reactor; second, wecollect many residual baits and feces in recirculating aquaculture system; then, we setup different concentration of TSS to culture flocs in biological flocculation reactor;what’s more, we feed the aquaculture animals with the flocs based on their variety.This paper mainly studies the effect on treatment effects of aquaculture solidparticles and nitrogen and phosphorus in recirculating aquaculture system by differentconcentration of TSS in freshwater and half of salt water at20salinity point. Accordingto the treatment effects, we choose the most appropriate TSS concentration. This papermainly includes:1. Treatment of aquaculture solid waste using Biofloc Technology in freshwater fish systemIn this experiment, we consider residual baits and feces in aquaculture system,glucose, ammonium chloride as nutrient source, carbon sources, as nitrogen source inbiological flocculation reactor respectively. We analyze and compare the treatmenteffects on aquaculture solid waste in fresh water in three experiment groups which TSSconcentrations are1500,2000,2500respectively. The results show that all experimentgroups can remove ammonia nitrogen effectively. On day4, ammonia nitrogen contentwas less than0.01mg/L in all groups. During the first10days, the contents of nitrateand nitrite were almost zero. After the day10, these three forms nitrogen stayed stability.After the day20, we did not regulate DOC/TAN, the contents of three nitrogen begansuccessively to rise in three experiment groups. After day32, we restored the controlabout DOC/TAN, the contents of three nitrogen began to decrease. During this process,the content trends of DOC and ammonia nitrogen were just reverse. From thisphenomenon, we can know the effect on the treatment of three forms of nitrogen byadding carbon source. The experiment results demonstrated that the third group wasbest in treatment of three nitrogen in freshwater.2. Treatment of aquaculture solid waste using Biofloc Technology in brackishwater fish systemIn this experiment we mainly compared and analysed the removal rate of nitrogenin two groups (TSS as1500mg/L and TSS as2500mg/L) in10L synthetized water at20salinity point.In early stage, the levels of three forms of nitrogen and total nitrogen all reachedthe maximum, and then three nitrogen content tended to reduce, and all reached theminimum on day15. During the period which forms day15to day20, the twoexperiment groups began to rise at first, afterwards tend to steady. However, three formsof nitrogen contents were all bounced during these two stages: one was from day25to27, the other was from day36to37. The experiment results indicated that second group’removal rate of nitrogen was better than the first group. This result, which was stillmore ideal, also demonstrated that the removal efficiency of nitrogen in brackish waterwas lower comparing with the fresh water. In this experiment, we also studied thetreatment efficiency of ammonia nitrogen and nitrite which concentration was at10mg/L,20mg/L and10mg/L respectively in brackish water in different TSSconcentration. From this result we can see that the contents of ammonia nitrogen were dropped fast at3.33mg per hour in two experiment groups, the content of nitritenitrogen was removal indirectly and slowly. Because nitrite nitrogen firstly wastransform to the form of ammonia nitrogen or nitrate, then was converted to the flocsprotein by Flocculation bacteria. Similar to the first experiment, this result also was thatthe second group is better in the treatment effect of aquaculture solid waste in brackishwater.3. Treatment of phosphate using Biofloc TechnologyThe change of phosphorus in the reaction activity of the previous period of time isin the normal growth of biological changes, besides half a buck in a began to release alot of phosphate, whether fresh water and half a buck, early in the reactor, theconsumption of phosphate, analyzes this is due to the early in the reactor in thelogarithm of microbial growth cycle period, in cell growth and proliferation ofphosphate normal growth of need. After the three groups of fresh water reactor water inthe phosphate content are rising,42days after in group1and2in water content ofphosphate overall has declined, and water in the phosphate group3has been in a higherlevel, this may be due to the reactor flocculation bacteria growth reached saturation,demand for phosphate to cap, and the release of the third group phosphate content more,can’t use, so the highest content in water, and group1phosphate release less, so thewater in phosphate content is low, it also explain, in fresh water group the flocculationstrains of phosphate demand is only in order to meet the needs of the growingproliferation, and the whole flocculation process on the phosphate needs are small, sothe use biological flocculation for the processing of phosphate effect is not obvious.And this conclusion also in half a buck experiment appears.On the basis of what we have discussed above,biological flocculation reactionprocess on the activated phosphate itself was not much remove use the effect, theexperimental process of phosphate reduce and increased because the reactor insidebacterial growth of phosphate normal proliferation demand it.